Squid Proxy - Website Content Acceleration and Distribution. Thousands of web-sites around the Internet use Squid to drastically increase their content delivery. Squid can reduce your server load and improve delivery speeds to clients.
Surge for Mac - Advanced Web Debugging Proxy for Mac & iOS
CCProxy - Want to share Internet connection? Get every computer online through a single Internet connection?
Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
3proxy - 3proxy freeware proxy server for Windows and Unix. HTTP, SOCKS, FTP, POP3
HTTP Toolkit - Beautiful, cross-platform & open-source tools to debug, test & build with HTTP(S). One-click setup for browsers, servers, Android, CLI tools, scripts and more.